Feeding device having control means, feed rollers, a pulse generator and a photoelectric device for directly measuring rate of feed of an elastic strip having marks thereon for a sewing machine

ABSTRACT

A feeding device for feeding elastic strip material to a sewing machine feeding a strip in response to one or more control signals. The strip feeder uses a feed roller having an associated pressure roller to provide a feed nip with the feeding roller, a sensor directly senses the rate of feed of the strip and generates one or more sensing signals. The sensor uses a signal generator which is a rotary pulse generator, or a photoelectric device for detecting marks on the strip. A controller receives the sensing signals and generates control signals for controlling the rate of feed of the strip.

FIELD OF THE INVENTION.

This invention relates to a feeding device for a sewing machine and moreparticularly concerns a feeding device which is adapted for feeding to asewing machine elastic strip material to be sewn into a garment.

DESCRIPTION OF PRIOR ART.

The elastic strip material may be of the type described in our U.KPatent No. 1406821; examples of suitable strip material are availableunder the registered Trade Marks "BONADEX", "TRICOFLEX" and "PLEATEX".

It is known to feed elastic strip material to a sewing machine throughguide means to fold a portion of a garment fabric around the strip readyfor sewing. It is also known to feed the strip to a sewing machine undertension so that after sewing into the garment it relaxes to produce anelasticated portion of the garment, e.g. a waistband.

Sometimes intermittent elastication is desired in a portion of a garmentand this can be achieved by sewing in discrete lengths of elastic stripmaterial or by using an intermittent tensioning technique such as thatdescribed in our copending application No. 8605501.

It is also known to control the tension in an elastic strip of materialbeing fed to a sewing machine in response to the speed of rotation of aportion of the sewing machine.

SUMMARY OF THE INVENTION.

It is an object of the present invention to provide an improved feedingdevice for feeding elastic strip material to a sewing machine.

According to the present invention a feeding device for feeding elasticstrip material to a sewing machine comprises strip feeding meansarranged to feed strip in response to one or more control signals,sensing means arranged to sense the rate of feed of the strip and togenerate one or more sensing signals and control means arranged toreceive said sensing signals and to generate control signals forcontrolling the strip feeding means.

The strip feeding means preferably comprises a roller having anassociated pressure roller to provide a feed nip with the feedingroller. The feeding roller may be driven by a motor which,advantageously, is a stepper motor.

The sensing means may also comprise a roller arranged to be rotated bythe strip as it is fed to the sewing machine. The roller may beconnected to a signal generator which is conveniently a rotary pulsegenerator.

Alternatively the sensing means may comprise detecting means arranged todetect features of the strip, or means associated with the strip, toproduce sensing signals dependent upon the rate of feed or extension ofthe strip. Such detecting means may, for example, be arranged to detectmarks on the strip which are spaced a predetermined distance apart whenthe strip is in a relaxed condition.

The control means is arranged to provide the desired control signals inresponse to sensing signals to adjust the feed rate to a required rate.

The control means is preferably an electronic signal processing devicehaving a display panel and may also be provided with adjusting means,conveniently manually operable adjusting means.

Conveniently the control means can be preset to provide a plurality ofpreset feed rates and switch means are provided to switch from onepreset feed rate to another. Such an arrangement enables an operator toswitch from one extension to a different extension in the strip fed tothe sewing machine, e.g. intermittent elastication. The switch means maybe controlled automatically according to a pre-programmed pattern, or byautomatic sensing, such as a position sensing device or stitch count.Alternatively it may be operator-controlled e.g. by means of aknee-switch, foot-switch or hand switch.

BRIEF DESCRIPTION OF THE DRAWINGS.

Reference is now made to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a device according to the inventionshown associated with a representation of a sewing machine in dashedlines; and

FIG. 2 is a schematic diagram of a pre-tensioning device for use withthe device of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

Referring to FIG. 1 a conventional sewing machine is shown in dashedlines at 10. The machine has a presser foot 11 to which an elastic stripmaterial 12 is fed together with a garment (not shown) by way of a guideand/or folding device located in the region 13.

The feed device comprises feeding means in the form of a knurled deviceroller 14 and associated knurled pressure roller 15, the device rollerbeing arranged to be driven by a stepper motor 16.

The sensing means comprises a roller 17 connected to a rotary pulsegenerator 18 which is capable of generating a series of signalsdetermined by the speed of rotation of the roller 17 and hence the feedrate of the strip 12.

The pulse generator 18 is connected to a control means 19 which iscapable of processing the sensing signals from the pulse generator 18 toproduce control signals which are passed to the stepper motor 16.

The pulse generator 18 includes a control panel 20 which includes anon/off switch 21 and three set switches, such as thumbwheel switches, 22which serve to pre-set three different extensions for the strip 12. Theknee-switch 23 serves to enable an operator to switch from one setswitch extension to the next. The set switch which is operated isindicated by illumination of the appropriate indicator light 24.

The device operates as follows. Actuation of the sewing machine 10causes elastic strip 12 to be drawn towards the presser foot 11. Theextension of the strip 12 is determined by the rate of feed which isgoverned by the rate of rotation of the stepper motor 16 and hence theroller 14. The pulse generator 18 measures the rate of feed of the strip12 and feeds sensing signals to the control unit which generates controlsignals to the stepper motor 16 to provide the appropriate feed rate togive a desired extension to the strip 12.

Where the device is used to provide intermittent elastication in, forexample, a waistband, elastic strip 12 is fed under a certain extensiondetermined by the setting of the control unit. When a non-elasticatedportion of the waistband is desired the control unit is switched to thenext setting (which may for example be zero extension) and the controlsignals generated will cause the stepper motor 16 to feed strip 12 at agreater rate until the extension of the strip is reduced to the desiredvalue (for example zero). As soon as the desired extension is achievedthe feed rate will be such as to maintain that extension until thecontrol unit setting is changed.

When the change of setting requires the extension of the strip to beincreased it is necessary to rotate the stepper motor 16 in the reversedirection until the desired extension is achieved. This may beinconvenient and an alternative way of increasing the extension could bepreferred. Such an alternative way could be to move the feed unit as awhole to provide the increased extension or to interpose an extensiondevice.

An example of a suitable extension device is shown diagrammatically inFIG. 2. A device 25 comprising a cylinder 26 and a rod 27 is connectedto a movable roller 28 disposed between two fixed rollers 29. The strip12 is fed between the rollers as shown in the drawing. It will be seenthat retraction of the rod 27 and the movable roller 28 to the positionshown in dashed lines will increase the extension of the strip 12 andextending the rod 27 will decrease the extension of the strip 12. Anyintermediate position can be chosen to give the desired extension.

The device according to the invention affords a number of advantagesover devices at present employed for feeding elastic strip to a sewingmachine. Prior feed devices have sensed a moving component of the sewingmachine such as the handwheel. This has the disadvantage that the feeddevice is not an independent unit. Furthermore, the device of thepresent invention is able to respond to the extension of the strip andis therefore accurate whereas the prior devices, which sense the sewingmachine, do not allow for variations in the rate of feed of the stripthrough the presser foot relative to the rate of rotation of thehandwheel, for example, due to machine wear, change of stitch-lengthsetting or slippage.

A further advantage of the device of the invention is that the elasticcan be fed independently of the operation of the sewing machine e.g. byhand, to avoid stitching at the start or finish of a waistband tofacilitate the finishing thereof.

Prior devices have also measured the tension in the strip e.g. by meansof a load cell. Load cells are not accurate over a wide range oftensions and also provide an analogue measurement. The device of thepresent invention provides digital measurement of rate of feed and adigital feed thereby ensuring greater accuracy.

In an alternative arrangement the pulse generator can be replaced by adevice, 30 e.g. a photoelectric device, which detects marks 31 providedon the elastic strip at a predetermined spacing. Furthermore, whilst astepper motor is preferred beacause of the precise control which can beachieved, other means may be used.

The device of the invention has the advantage that it can be used withdifferent sewing machines without any modification of the machines beingrequired. Furthermore, whilst the device has been described specificallyfor use in feeding elastic strip to a sewing machine it can be used tofeed other devices for example in the manufacture of the elastic strip.

I claim:
 1. A feeding device for feeding elastic strip material to asewing machine comprises strip feeding means arranged to feed strip inresponse to at least one control signals, sensing means arranged todirectly sense the rate of feed of the strip and to generate at leastone sensing signals and control means arranged to receive said sensingsignals and generate control signals for controlling the strip feedingmeans.
 2. A feeding device according to claim 1 wherein the stripfeeding means comprises a roller having an associated pressure roller toprovide a feed nip with the strip feeding roller.
 3. A feeding deviceaccording to claim 2 wherein the strip feeding roller is driven by amotor.
 4. A feeding device according to claim 3 wherein the motor is astepper motor.
 5. A feeding device according to claim 1 wherein thesensing means also comprises a roller arranged to be rotated by thestrip being fed to the sewing machine.
 6. A feeding device according toclaim 5 wherein the roller is connected to a signal generator.
 7. Afeeding device according to claim 5 wherein the signal generator is arotary pulse generator.
 8. A feeding device according to claim 1 whereinthe sensing means comprises detecting means arranged to detect physicalfeatures present on the strip to produce sensing signals dependent uponthe rate of feed.
 9. A feeding device according to claim 8 wherein thedetecting means is arranged to detect marks on the strip spaced apredetermined distance apart when the strip is in a relaxed condition.10. A feeding device according to claim 1 wherein the control means isarranged to provide the desired control signals in response to said atleast one sensing signal to adjust the feed rate to a required rate. 11.A feeding device according to claim 10 wherein the control means ispresettable to provide a plurality of preset feed rates and switch meansare provided to switch from one preset feed rate to another.
 12. Afeeding device according to claim 11 wherein the switch means iscontrolled automatically according to a pre-programmed pattern.
 13. Afeeding device according to claim 11 in which the switching means iscontrolled by automatic sensing.
 14. A feeding device according to claim13 in which the switch means is controlled automatically according to aposition sensing device.
 15. A feeding device according to claim 13 inwhich the switch means is controlled automatically according to a switchcount.
 16. A feeding device according to claim 1 wherein the controlmeans is in an electronic signal processing device having a displaypanel.
 17. A feeding device according to claim 16 wherein the electronicsignal processing device is provided with an adjusting means, saidadjusting means is a manually operable adjusting means.
 18. Incombination a feeding device for feeding elastic strip material to asewing machine the device comprising strip feeding means arranged tofeed strip in response to at least one control signal, sensing meansarranged to sense the rate of feed of the strip and to generate at leastone sensing signal and control means arranged to receive said sensingsignals and to generate control signals for controlling the stripfeeding means wherein the sensing means comprises detecting meansarranged to detect marks on the strip spaced a predetermined distanceapart when the strip is in a relaxed condition whereby to producesensing signals dependent on the rate of feed, said strip feeding meansincluding a strip, the strip having marks thereon spaced a predetermineddistance apart when the strip is in a relaxed condition.